1. Field of the Invention
The present invention relates to a display device and a display control method, particularly to a display device and a display control method for reducing flicker of images.
2. Description of the Related Art
A liquid crystal display (LCD) device includes a liquid crystal panel having a color filter substrate colored with R (red), G (green), and B (blue) and a liquid crystal layer; and a backlight placed on the back side thereof.
In the LCD device, twist of liquid crystal molecules in the liquid crystal layer is controlled by changing a voltage. Light beams from the backlight passed through the liquid crystal layer in accordance with the twist of the liquid crystal molecules pass through the color filter substrate, colored with R, G, and B, so that each of the light beams becomes an R, G, or B light beam. Accordingly,
In the following description, changing the transmittance of light by controlling twist of liquid crystal molecules by changing a voltage is referred to as “control of an aperture ratio”. The brightness of light emitted from the backlight serving as a light source is called “emission brightness”, whereas the brightness of light emitted from the front surface of the liquid crystal panel, that is, the intensity of light recognized by a user seeing a displayed image, is called “display brightness”.
In a conventional LCD device, the backlight evenly lights the entire screen of the liquid crystal panel with (substantially) maximum intensity, and only the aperture ratio of each pixel in the liquid crystal panel is controlled so that a required display brightness can be obtained in each pixel of the screen. In this case, the backlight emits light with maximum emission brightness even if the entire screen is dark, which causes a problem of high power consumption.
As countermeasures against this problem, there is suggested a method of dividing a screen into a plurality of areas and controlling the emission brightness of the backlight in units of the areas (e.g., see Patent Documents 1 and 2: Japanese Unexamined Patent Application Publication Nos. 2004-212503 and 2004-246117).
The control of backlight according to these known arts is described with reference to FIGS. 1A to 1C.
FIG. 1A shows an original image P1 displayed in an LCD device. The original image P1 has an oval darkest area R1 at the center thereof. The image is lighter toward the outer side of the area R1.
FIG. 1B shows a simplified configuration of the backlight.
In the backlight shown in FIG. 1B, the light emission area has 24 areas, that is, 4 areas in the horizontal direction×6 areas in the vertical direction.
When the backlight shown in FIG. 1B emits light corresponding to the original image P1, the backlight suppresses the emission brightness of the two shaded areas in FIG. 1B (darkened).
As a result, in the entire backlight, the distribution of emission brightness shown in FIG. 1C can be obtained for the original image P1 shown in FIG. 1A, and the part of the backlight corresponding to the darkest area R1 is darkened. Accordingly, the power consumption is reduced.